Method for transmitting downlink control information in wireless communication system and device using same

ABSTRACT

Provided are a method for transmitting downlink control information (DCI) in a wireless communication system and a device using same. The method enables determining the size of a first DCI format and adjusting the size of a second DCI format so as to be the same as the size of the first DCI format, wherein the first DCI format and the second DCI format are DCI formats sharing the same search space regardless of whether the formats are for the same serving cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/328,658, filed on Feb. 26, 2019, which is the National Stage filingunder 35 U.S.C. 371 of International Application No. PCT/KR2017/009510,filed on Aug. 30, 2017, which claims the benefit of U.S. ProvisionalApplication No. 62/381,055, filed on Aug. 30, 2016, 62/381,634, filed onAug. 31, 2016, 62/382,311, filed on Sep. 1, 2016, 62/383,385, filed onSep. 2, 2016, 62/384,163, filed on Sep. 6, 2016, 62/416,714, filed onNov. 3, 2016, 62/420,732, filed on Nov. 11, 2016, and 62/450,580, filedon Jan. 26, 2017, the contents of which are all hereby incorporated byreference herein in their entireties.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to wireless communications, and moreparticularly, relates to a method for transmitting downlink controlinformation in a wireless communication system and an apparatus usingthe method.

Related Art

In International Telecommunication Union Radio communication sector(ITU-R), a standardization task for International MobileTelecommunication (IMT)-Advanced, that is, the next-generation mobilecommunication system since the third generation, is in progress.IMT-Advanced sets its goal to support Internet Protocol (IP)-basedmultimedia services at a data transfer rate of 1 Gbps in the stop andslow-speed moving state and of 100 Mbps in the fast-speed moving state.

For example, 3^(rd) Generation Partnership Project (3GPP) is a systemstandard to satisfy the requirements of IMT-Advanced and is preparingfor LTE-Advanced improved from Long Term Evolution (LTE) based onOrthogonal Frequency Division Multiple Access (OFDMA)/SingleCarrier-Frequency Division Multiple Access (SC-FDMA) transmissionschemes. LTE-Advanced is one of strong candidates for IMT-Advanced.

The 3GPP has been conducting studies on V2X as one study item (SI) forLTE Release 14. V2X refers to vehicle-to-everything communication andincludes V2V, that is, vehicle-to-vehicle communication.

Among various methods for performing V2V communication, there is amethod in which a base station (BS) schedules a resource for V2Vcommunication. When this method is used, a BS transmits a new type ofdownlink control information for V2V communication to a user equipment(UE).

A method for configuring downlink control information for V2Vcommunication is need which is capable of minimizing an increase in thenumber of times of blind decoding by a UE without considerablyincreasing complexity.

SUMMARY OF THE INVENTION

An aspect of the present invention is to provide a method fortransmitting downlink control information in a wireless communicationsystem, and an apparatus using the same.

In one aspect, provided is a method for transmitting downlink controlinformation (DCI) in a wireless communication system. The methodincludes determining a size of a first DCI format and adjusting a sizeof a second DCI format to be equal to the size of the first DCI format.The first DCI format and the second DCI format are DCI formats sharingthe same search space regardless of the DCI formats are for the sameserving cell.

The first DCI format may be a DCI format used for sidelinksemi-persistent scheduling, and the second DCI format may be a DCIformat used for sidelink dynamic scheduling. In this case, DCI format 0may not be transmitted in the search space.

The first DCI format may be DCI format 0 used for scheduling of aphysical uplink shared channel (PUSCH).

The second DCI format may be DCI format 5A used for scheduling of aphysical sidelink control channel (PSCCH).

The first DCI format and the second DCI format may be DCI formats forscheduling physical channels of different serving cells.

The first DCI format and the second DCI format may share the same searchspace by having the same carrier indication field (CIF) value.

When the second DCI format is DCI format 5A, a payload size of DCIformat 5A may vary depending on a number of subchannels configured for auser equipment.

The subchannels may comprise a plurality of contiguous resource blocks(RBs).

When the first DCI format is DCI format 0 and the second DCI format isDCI format 5A, the DCI format 5A having a greater size than that of theDCI format 0 is not transmitted in the search space.

In another aspect, provided is a device for transmitting downlinkcontrol information (DCI) in a wireless communication system. The deviceincludes a radio frequency (RF) unit to transmit and receive a radiosignal and a processor connected to the RF unit to operate. Theprocessor determines a size of a first DCI format and adjusts a size ofa second DCI format to be equal to the size of the first DCI format, andthe first DCI format and the second DCI format are DCI formats sharingthe same search space regardless of the formats are for the same servingcell.

In configuring downlink control information for V2V communication, it ispossible to prevent complexity in UE implementing V2X communication frombeing considerably increased. For example, it is possible to minimize orprevent an increase in the number of times of blind decoding by a UE fordetecting downlink control information for V2X communication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 is a diagram showing a wireless protocol architecture for a userplane.

FIG. 3 is a diagram showing a wireless protocol architecture for acontrol plane.

FIG. 4 shows a basic structure for ProSe.

FIG. 5 shows the deployment examples of types of UE performing ProSedirect communication and cell coverage.

FIG. 6 illustrates scenarios in which V2V communication is performed.

FIG. 7 illustrates a signaling process for V2V communication between UEsand a BS.

FIG. 8 illustrates a signaling process for V2V communication betweenUEs.

FIG. 9 illustrates a method for determining the payload size of DCIformat 5A according to proposed method #1.

FIG. 10 illustrate a size fitting method for DCI format 1A according tothe prior art.

FIG. 11 conceptually illustrates a size fitting method for DCI format 5Aaccording to proposed method #3.

FIG. 12 illustrates a generalized size fitting method for a DCI formataccording to proposed method #3.

FIG. 13 illustrates a specific example of applying FIG. 12.

FIG. 14 illustrates an operation method of a UE in a search space.

FIG. 15 illustrate a DCI size fitting method according to example #4-4.

FIG. 16 illustrates sidelink cross-carrier scheduling timing.

FIG. 17 is a block diagram illustrating a device to implement anembodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows a wireless communication system.

The wireless communication system may be referred to as an Evolved-UMTSTerrestrial Radio Access Network (E-UTRAN) or a Long Term Evolution(LTE)/LTE-A system, for example.

The E-UTRAN includes at least one base station (BS) 20 which provides acontrol plane and a user plane to a user equipment (UE) 10. The UE 10may be fixed or mobile, and may be referred to as another terminology,such as a mobile station (MS), a user terminal (UT), a subscriberstation (SS), a mobile terminal (MT), a wireless device, etc. The BS 20is generally a fixed station that communicates with the UE 10 and may bereferred to as another terminology, such as an evolved node-B (eNB), abase transceiver system (BTS), an access point, etc.

The BSs 20 are interconnected by means of an X2 interface. The BSs 20are also connected by means of an S1 interface to an evolved packet core(EPC) 30, more specifically, to a mobility management entity (MME)through S1-MME and to a serving gateway (S-GW) through S1-U.

The EPC 30 includes an MME, an S-GW, and a packet data network-gateway(P-GW). The MME has access information of the UE or capabilityinformation of the UE, and such information is generally used formobility management of the UE. The S-GW is a gateway having an E-UTRANas an end point. The P-GW is a gateway having a PDN as an end point.

Layers of a radio interface protocol between the UE and the network canbe classified into a first layer (L1), a second layer (L2), and a thirdlayer (L3) based on the lower three layers of the open systeminterconnection (OSI) model that is well-known in the communicationsystem. Among them, a physical (PHY) layer belonging to the first layerprovides an information transfer service by using a physical channel,and a radio resource control (RRC) layer belonging to the third layerserves to control a radio resource between the UE and the network. Forthis, the RRC layer exchanges an RRC message between the UE and the BS.

FIG. 2 is a diagram showing a wireless protocol architecture for a userplane. FIG. 3 is a diagram showing a wireless protocol architecture fora control plane. The user plane is a protocol stack for user datatransmission. The control plane is a protocol stack for control signaltransmission.

Referring to FIGS. 2 and 3, a PHY layer provides an upper layer with aninformation transfer service through a physical channel. The PHY layeris connected to a medium access control (MAC) layer which is an upperlayer of the PHY layer through a transport channel. Data is transferredbetween the MAC layer and the PHY layer through the transport channel.The transport channel is classified according to how and with whatcharacteristics data is transferred through a radio interface.

Data is moved between different PHY layers, that is, the PHY layers of atransmitter and a receiver, through a physical channel. The physicalchannel may be modulated according to an Orthogonal Frequency DivisionMultiplexing (OFDM) scheme, and use the time and frequency as radioresources.

The functions of the MAC layer include mapping between a logical channeland a transport channel and multiplexing and demultiplexing to atransport block that is provided through a physical channel on thetransport channel of a MAC Service Data Unit (SDU) that belongs to alogical channel. The MAC layer provides service to a Radio Link Control(RLC) layer through the logical channel.

The functions of the RLC layer include the concatenation, segmentation,and reassembly of an RLC SDU. In order to guarantee various types ofQuality of Service (QoS) required by a Radio Bearer (RB), the RLC layerprovides three types of operation mode: Transparent Mode (TM),Unacknowledged Mode (UM), and Acknowledged Mode (AM). AM RLC provideserror correction through an Automatic Repeat Request (ARQ).

The RRC layer is defined only on the control plane. The RRC layer isrelated to the configuration, reconfiguration, and release of radiobearers, and is responsible for control of logical channels, transportchannels, and PHY channels. An RB means a logical route that is providedby the first layer (PHY layer) and the second layers (MAC layer, the RLClayer, and the PDCP layer) in order to transfer data between UE and anetwork.

The function of a Packet Data Convergence Protocol (PDCP) layer on theuser plane includes the transfer of user data and header compression andciphering. The function of the PDCP layer on the user plane furtherincludes the transfer and encryption/integrity protection of controlplane data.

What an RB is configured means a process of defining the characteristicsof a wireless protocol layer and channels in order to provide specificservice and configuring each detailed parameter and operating method. AnRB can be divided into two types of a Signaling RB (SRB) and a Data RB(DRB). The SRB is used as a passage through which an RRC message istransmitted on the control plane, and the DRB is used as a passagethrough which user data is transmitted on the user plane.

If RRC connection is established between the RRC layer of UE and the RRClayer of an E-UTRAN, the UE is in the RRC connected state. If not, theUE is in the RRC idle state.

A downlink transport channel through which data is transmitted from anetwork to UE includes a broadcast channel (BCH) through which systeminformation is transmitted and a downlink shared channel (SCH) throughwhich user traffic or control messages are transmitted. Traffic or acontrol message for downlink multicast or broadcast service may betransmitted through the downlink SCH, or may be transmitted through anadditional downlink multicast channel (MCH). Meanwhile, an uplinktransport channel through which data is transmitted from UE to a networkincludes a random access channel (RACH) through which an initial controlmessage is transmitted and an uplink shared channel (SCH) through whichuser traffic or control messages are transmitted.

Logical channels that are placed over the transport channel and that aremapped to the transport channel include a broadcast control channel(BCCH), a paging control channel (PCCH), a common control channel(CCCH), a multicast control channel (MCCH), and a multicast trafficchannel (MTCH).

The physical channel includes several OFDM symbols in the time domainand several subcarriers in the frequency domain. One subframe includes aplurality of OFDM symbols in the time domain. An RB is a resourcesallocation unit, and includes a plurality of OFDM symbols and aplurality of subcarriers. Furthermore, each subframe may use specificsubcarriers of specific OFDM symbols (e.g., the first OFDM symbol) ofthe corresponding subframe for a physical downlink control channel(PDCCH), that is, an L1/L2 control channel. A Transmission Time Interval(TTI) is a unit time for subframe transmission.

The RRC state means whether or not the RRC layer of UE is logicallyconnected to the RRC layer of the E-UTRAN. A case where the RRC layer ofUE is logically connected to the RRC layer of the E-UTRAN is referred toas an RRC connected state. A case where the RRC layer of UE is notlogically connected to the RRC layer of the E-UTRAN is referred to as anRRC idle state. The E-UTRAN may check the existence of corresponding UEin the RRC connected state in each cell because the UE has RRCconnection, so the UE may be effectively controlled. In contrast, theE-UTRAN is unable to check UE in the RRC idle state, and a Core Network(CN) manages UE in the RRC idle state in each tracking area, that is,the unit of an area greater than a cell. That is, the existence ornon-existence of UE in the RRC idle state is checked only for each largearea. Accordingly, the UE needs to shift to the RRC connected state inorder to be provided with common mobile communication service, such asvoice or data.

When a user first powers UE, the UE first searches for a proper cell andremains in the RRC idle state in the corresponding cell. The UE in theRRC idle state establishes RRC connection with an E-UTRAN through an RRCconnection procedure when it is necessary to set up the RRC connection,and shifts to the RRC connected state. A case where UE in the RRC idlestate needs to set up RRC connection includes several cases. Forexample, the cases may include a need to send uplink data for a reason,such as a call attempt by a user, and to send a response message as aresponse to a paging message received from an E-UTRAN.

A Non-Access Stratum (NAS) layer placed over the RRC layer performsfunctions, such as session management and mobility management.

In the NAS layer, in order to manage the mobility of UE, two types ofstates: EPS Mobility Management-REGISTERED (EMM-REGISTERED) andEMM-DEREGISTERED are defined. The two states are applied to UE and theMME. UE is initially in the EMM-DEREGISTERED state. In order to access anetwork, the UE performs a process of registering it with thecorresponding network through an initial attach procedure. If the attachprocedure is successfully performed, the UE and the MME become theEMM-REGISTERED state.

In order to manage signaling connection between UE and the EPC, twotypes of states: an EPS Connection Management (ECM)-IDLE state and anECM-CONNECTED state are defined. The two states are applied to UE andthe MME. When the UE in the ECM-IDLE state establishes RRC connectionwith the E-UTRAN, the UE becomes the ECM-CONNECTED state. The MME in theECM-IDLE state becomes the ECM-CONNECTED state when it establishes S1connection with the E-UTRAN. When the UE is in the ECM-IDLE state, theE-UTRAN does not have information about the context of the UE.Accordingly, the UE in the ECM-IDLE state performs procedures related toUE-based mobility, such as cell selection or cell reselection, without aneed to receive a command from a network. In contrast, when the UE is inthe ECM-CONNECTED state, the mobility of the UE is managed in responseto a command from a network. If the location of the UE in the ECM-IDLEstate is different from a location known to the network, the UE informsthe network of its corresponding location through a tracking area updateprocedure.

Hereinafter, a D2D operation will be described. In 3GPP LTE-A, a servicerelated to the D2D operation is referred to as a proximity-based service(ProSe). Hereinafter, a ProSe is conceptually equivalent to a D2Doperation and may be interchangeable with a D2D operation. Sidelinkcommunication may be referred to as different terms, such as D2Dcommunication, ProSe direct communication, and ProSe communication.Sidelink discovery may be referred to as different terms, such as D2Ddiscovery, ProSe direct discovery, and ProSe discovery. Hereinafter,ProSe is described. A D2D operation is performed between UEs, in whichan interface between the UEs may be referred to as a sidelink. Asidelink is a UE-to-UE interface for sidelink communication and sidelinkdiscovery and corresponds to a PC5 interface.

The ProSe includes ProSe direction communication and ProSe directdiscovery. The ProSe direct communication is communication performedbetween two or more proximate UEs. The UEs may perform communication byusing a protocol of a user plane. A ProSe-enabled UE implies a UEsupporting a procedure related to a requirement of the ProSe. Unlessotherwise specified, the ProSe-enabled UE includes both of a publicsafety UE and a non-public safety UE. The public safety UE is a UEsupporting both of a function specified for a public safety and a ProSeprocedure, and the non-public safety UE is a UE supporting the ProSeprocedure and not supporting the function specified for the publicsafety.

ProSe direct discovery is a process for discovering anotherProSe-enabled UE adjacent to ProSe-enabled UE. In this case, only thecapabilities of the two types of ProSe-enabled UE are used. EPC-levelProSe discovery means a process for determining, by an EPC, whether thetwo types of ProSe-enabled UE are in proximity and notifying the twotypes of ProSe-enabled UE of the proximity.

Hereinafter, for convenience, the ProSe direct communication may bereferred to as D2D communication, and the ProSe direct discovery may bereferred to as D2D discovery.

FIG. 4 shows a basic structure for ProSe.

Referring to FIG. 4, the basic structure for ProSe includes an E-UTRAN,an EPC, a plurality of types of UE including a ProSe applicationprogram, a ProSe application server (a ProSe APP server), and a ProSefunction.

The EPC represents an E-UTRAN core network configuration. The EPC mayinclude an MME, an S-GW, a P-GW, a policy and charging rules function(PCRF), a home subscriber server (HSS) and so on.

The ProSe APP server is a user of a ProSe capability for producing anapplication function. The ProSe APP server may communicate with anapplication program within UE.

The application program within UE may use a ProSe capability forproducing an application function.

The ProSe function may include at least one of the followings, but isnot necessarily limited thereto.

-   -   Interworking via a reference point toward the 3rd party        applications    -   Authorization and configuration of UE for discovery and direct        communication    -   Enable the functionality of EPC level ProSe discovery    -   ProSe related new subscriber data and handling of data storage,        and also handling of the ProSe identities    -   Security related functionality    -   Provide control towards the EPC for policy related functionality    -   Provide functionality for charging (via or outside of the EPC,        e.g., offline charging)

A reference point and a reference interface in the basic structure forProSe are described below.

-   -   PC1: a reference point between the ProSe application program        within the UE and the ProSe application program within the ProSe        APP server. This is used to define signaling requirements in an        application dimension.    -   PC2: a reference point between the ProSe APP server and the        ProSe function. This is used to define an interaction between        the ProSe APP server and the ProSe function. The update of        application data in the ProSe database of the ProSe function may        be an example of the interaction.    -   PC3: a reference point between the UE and the ProSe function.        This is used to define an interaction between the UE and the        ProSe function. A configuration for ProSe discovery and        communication may be an example of the interaction.    -   PC4: a reference point between the EPC and the ProSe function.        This is used to define an interaction between the EPC and the        ProSe function. The interaction may illustrate the time when a        path for 1:1 communication between types of UE is set up or the        time when ProSe service for real-time session management or        mobility management is authenticated.    -   PC5: a reference point used for using control/user plane for        discovery and communication, relay, and 1:1 communication        between types of UE.    -   PC6: a reference point for using a function, such as ProSe        discovery, between users belonging to different PLMNs.    -   SGi: this may be used to exchange application data and types of        application dimension control information.

The D2D operation may be supported both when UE is serviced within thecoverage of a network (cell) or when it is out of coverage of thenetwork.

FIG. 5 shows the deployment examples of types of UE performing ProSedirect communication and cell coverage.

Referring to FIG. 5(a), types of UE A and B may be placed outside cellcoverage. Referring to FIG. 5(b), UE A may be placed within cellcoverage, and UE B may be placed outside cell coverage. Referring toFIG. 5(c), types of UE A and B may be placed within single cellcoverage. Referring to FIG. 5(d), UE A may be placed within coverage ofa first cell, and UE B may be placed within coverage of a second cell.

ProSe direct communication may be performed between types of UE placedat various positions as in FIG. 5.

<Radio Resource Allocation for D2D Communication (ProSe DirectCommunication)>.

At least one of the following two modes may be used for resourceallocation for D2D communication.

1. Mode 1

Mode 1 is mode in which resources for ProSe direct communication arescheduled by an eNB. UE needs to be in the RRC_CONNECTED state in orderto send data in accordance with mode 1. The UE requests a transmissionresource from an eNB. The eNB performs scheduling assignment andschedules resources for sending data. The UE may send a schedulingrequest to the eNB and send a ProSe Buffer Status Report (BSR). The eNBhas data to be subjected to ProSe direct communication by the UE basedon the ProSe BSR and determines that a resource for transmission isrequired.

2. Mode 2

Mode 2 is mode in which UE directly selects a resource. UE directlyselects a resource for ProSe direct communication in a resource pool.The resource pool may be configured by a network or may have beenpreviously determined.

Meanwhile, if UE has a serving cell, that is, if the UE is in theRRC_CONNECTED state with an eNB or is placed in a specific cell in theRRC_IDLE state, the UE is considered to be placed within coverage of theeNB.

If UE is placed outside coverage, only mode 2 may be applied. If the UEis placed within the coverage, the UE may use mode 1 or mode 2 dependingon the configuration of an eNB.

If another exception condition is not present, only when an eNB performsa configuration, UE may change mode from mode 1 to mode 2 or from mode 2to mode 1.

<D2D Discovery (ProSe Direct Discovery)>

D2D discovery refers to the procedure used in a ProSe capable terminaldiscovering other ProSe capable terminals in close proximity thereto andmay be referred to as ProSe direct discovery. The information used forProSe direct discovery is hereinafter referred to as discoveryinformation.

A PC 5 interface may be used for D2D discovery. The PC 5 interfaceincludes an MAC layer, a PHY layer, and a ProSe Protocol layer, that is,a higher layer. The higher layer (the ProSe Protocol) handles thepermission of the announcement and monitoring of discovery information.The contents of the discovery information are transparent to an accessstratum (AS). The ProSe Protocol transfers only valid discoveryinformation to the AS for announcement. The MAC layer receives discoveryinformation from the higher layer (the ProSe Protocol). An IP layer isnot used to send discovery information. The MAC layer determines aresource used to announce discovery information received from the higherlayer. The MAC layer produces an MAC protocol data unit (PDU) forcarrying discovery information and sends the MAC PDU to the physicallayer. An MAC header is not added.

In order to announce discovery information, there are two types ofresource assignment.

1. Type 1

The type 1 is a method for assigning a resource for announcing discoveryinformation in a UE-not-specific manner. An eNB provides a resource poolconfiguration for discovery information announcement to types of UE. Theconfiguration may be broadcasted through the SIB. The configuration maybe provided through a UE-specific RRC message. Or the configuration maybe broadcasted through other than the RRC message in other layer or maybe provided by UE-specific signaling.

UE autonomously selects a resource from an indicated resource pool andannounces discovery information using the selected resource. The UE mayannounce the discovery information through a randomly selected resourceduring each discovery period.

2. Type 2

The type 2 is a method for assigning a resource for announcing discoveryinformation in a UE-specific manner. UE in the RRC_CONNECTED state mayrequest a resource for discovery signal announcement from an eNB throughan RRC signal. The eNB may announce a resource for discovery signalannouncement through an RRC signal. A resource for discovery signalmonitoring may be assigned within a resource pool configured for typesof UE.

An eNB 1) may announce a type 1 resource pool for discovery signalannouncement to UE in the RRC_IDLE state through the SIB. Types of UEwhose ProSe direct discovery has been permitted use the type 1 resourcepool for discovery information announcement in the RRC_IDLE state.Alternatively, the eNB 2) announces that the eNB supports ProSe directdiscovery through the SIB, but may not provide a resource for discoveryinformation announcement. In this case, UE needs to enter theRRC_CONNECTED state for discovery information announcement.

An eNB may configure that UE has to use a type 1 resource pool fordiscovery information announcement or has to use a type 2 resourcethrough an RRC signal in relation to UE in the RRC_CONNECTED state.

Hereinafter, the present invention will be described.

The present invention proposes a method and a device for transmittingdownlink control information (DCI) in a wireless communication system.

Hereinafter, a UE refers to a terminal of a user. However, when networkequipment, such as a BS, transmits or receives a signal according to thecommunication mode between UEs, the network equipment may also beregarded as a UE.

For the convenience of description, abbreviations used in the presentinvention are described.

A PSBCH represents a physical sidelink broadcast channel. A PSCCHrepresents a physical sidelink control channel. A PSDCH represents aphysical sidelink discovery channel. A PSSCH represents a physicalsidelink shared channel. An SLSS represents a sidelink synchronizationsignal. An SLSS includes a primary sidelink synchronization signal(PSSS) and a secondary sidelink synchronization signal (SSSS).

As described above, a sidelink refers to a UE-to-UE interface for D2Dcommunication and D2D discovery. A sidelink corresponds to a PC5interface. D2D communication may be referred to as sidelinkcommunication or simply as communication, and D2D discovery may bereferred to as sidelink discovery or simply as discovery. A D2D UErefers to a UE that performs a D2D operation, and a D2D operationincludes at least one of D2D communication and D2D discovery.

Hereinafter, for the convenience of description, the present inventionwill be described based on 3GPP LTE/LTE-A systems. However, the presentinvention may also be applicable to systems other than the 3GPPLTE/LTE-A systems.

The present invention may also be applied to vehicle-to-everything (V2X)communication. V2X communication refers to a communication mode ofexchanging or sharing information, such as traffic conditions, throughcommunication with road infrastructure and other vehicles while driving.V2X may include vehicle-to-vehicle (V2V), which refers to communicationbetween vehicles, vehicle-to-pedestrian (V2P), which refers tocommunication between UEs carried by a vehicle and an individual person,and vehicle-to-infrastructure/network (V2I/N), which refers tocommunication between a vehicle and a roadside unit (RSU) and a network.Hereinafter, V2V is illustrated as an example of V2X communication, butthe present invention is not limited thereto.

UE operations related to V2V communication will be described. V2Vcommunication refers to communication between a UE installed in a firstvehicle and a UE installed in a second vehicle.

FIG. 6 illustrates scenarios in which V2V communication is performed.

Referring to FIG. 6, V2V communication may be performed in: 1) scenario1 where only a V2V operation based on PC5, which is an interface betweenUEs, is supported; 2) scenario 2 where only a V2V operation based on Uu,which is an interface between a BS (eNodeB) and a UE, is supported; and3) scenario 3 where a V2V operation is supported using both PC5 and Uu.

FIG. 7 illustrates a signaling process for V2V communication between UEsand a BS.

Referring to FIG. 7, a BS transmits a DCI format to UE #1 (S70). The DCIformat may be a DCI format for mode 1, that is, a mode in which the BSschedules a resource for V2V communication. UE #1 may perform sidelinkcommunication, for example, V2V communication, with UE #2 using theresource scheduled according to the DCI format (S71).

FIG. 8 illustrates a signaling process for V2V communication betweenUEs.

Referring to FIG. 8, UE #1 transmits a sidelink control information(SCI) format for V2V communication (S80). Subsequently, UE #1 mayperform V2V communication with UE #2 on the basis of the SCI format(S81).

Regarding V2V communication, when a scheduling assignment (SA) and dataassociated with the SA are transmitted in the same subframe, a resourceindicated by decoding the SA or reserved or a resource having a PSSCHRSRP of a threshold value or greater among resources for the associateddata may be excluded.

Here, PSSCH RSRP in the resources for the associated data may be definedas the linear average of power distribution of resource elementscarrying a DM RS associated with an associated PSSCH in PRBs indicatedby the PSCCH.

A reference point for PSSCH RSRP may be an antenna connector of a UE.

For SA decoding, a UE may perform the following operations.

Resource selection/reselection may be triggered for the UE in a subframe(hereinafter, also referred to as a TTI) #n. Then, the UE may sense fromsubframe #n-a to subframe #n-b (a>b>0, where a and b are an integer) andmay select/reselect a resource for transmission of a V2V message basedon the sensing result.

Values a and b may be set commonly to UEs or may be set independentlyfor UEs.

When a and b are common values to UEs, for example, ‘a=1000+b’. That is,when the UE is triggered to autonomously select a resource fortransmission of a V2V message, the UE may perform a sensing operationfor one second (1000 ms=1000 subframes=1000 TTIs).

The UE may consider SAs of other UEs in an interval from subframe #n-ato subframe #n-b. The SA may be associated with data transmission in theinterval from subframe #n-a to subframe #n-b and may be transmittedbefore subframe #n-a.

When the UE does not perform a sensing operation in subframe #m (forexample, since a signal is transmitted in subframe #m), the UE mayexclude subframes #(m+100*k) from resource selection/reselection. The UEmay not perform but skip a sensing operation in subframes that are usedfor the UE to transmit a signal.

After performing sensing, the UE selects a time/frequency resource for aPSSCH, that is, a sidelink data channel.

Alternatively, upon decoding an SA in subframe (TTI) #m+c in a sensingperiod, a first UE may assume that the same frequency resource is alsoreserved in subframe #m+d+P*i by a second UE transmitting the SA. Here,P may be a fixed value of 100, and i may be selected from among [0, 1, .. . , 10] and may be carrier-specifically limited. Alternatively, i maybe set to 0, which means that it is not intended to reserve a frequencyresource. The value of i may be signaled via a 4-bit field in the SA.

When candidate semi-persistent resource X having a P*I period collideswith resource Y reserved by an SA of another UE and satisfies athreshold condition, the UE may exclude resource X. I may be a value fori signaled via the SA.

When resources remaining after excluding resources via SA decoding andsensing are less than 20% of the total resources in a selected window,the UE may increase a threshold (e.g., 3 dB) and may then exclude aresource again, in which excluding resources may be performed until theremaining resources are greater than 20% of the total resources in theselected window.

The measurement period of the PSSCH resource may be P. The measurementmay be performed only on resources remaining via the foregoing process.

In a process of selecting a V2V transmission resource after excluding aparticular resource, when a counter reaches 0, the UE may maintain acurrent resource with a probability of p and may reset the counter. Thatis, a resource may be reselected with a probability of 1−p. Acarrier-specific parameter p may be preset and may be set in a range of[0, 0.2, 0.4, 0.6, 0.8].

The UE measures the remaining PSSCH resources excluding the particularresource, ranks the resources on the basis of the total receptionenergy, and then selects a subset thereof. The subset may be a set ofcandidate resources having the lowest reception energy. The size of thesubset may be 20% of the total resources in the selected window.

The UE may randomly select one resource from the subset.

When only one transmission block is transmitted in one subframe, the UEmay select M consecutive subchannels, and the average of energy measuredin each subchannel may be an energy measurement of each resource.

When a transmission block is transmitted in two subframes, the followingresource selection methods may be supported. One resource may beselected using a mechanism defined for a case where a transmission blockis transmitted in one subframe. Alternatively, when a particularcondition is satisfied, it is possible to randomly select anotherresource.

The UE may not transmit a transmission block without an SA. That is, anSA also needs to be transmitted in TB transmission or retransmission.

When a resource is set such that an SA and data can be transmitted inthe same subframe, the UE does not expect to combine the resource with aPSCCH transmitted in another subframe.

When a resource is set such that an SA and data are always transmittedvia contiguous resource blocks in the same subframe, a subchannel havingthe lowest index among subchannels selected for data transmission isused for SA transmission. A resource pool may include one subchannel ora plurality of subchannels in the frequency domain. A subchannel mayinclude consecutive resource blocks in the same subframe. The size of asubchannel, that is, the number of resource blocks included thesubchannel, may be one of {5, 6, 10, 15, 20, 25, 50, 75, 100} and may bepredetermined or may be set by a BS. Each subchannel may include one SAcandidate resource. The SA candidate resource may also be used for datatransmission.

When a resource is set such that an SA and data are transmitted vianoncontiguous resource blocks in the same subframe, the number ofsubchannels in an associated data resource pool and the number of SAcandidate resources in an SA resource pool may be the same. The SAcandidate resources in the SA resource pool and the subchannels in thedata resource pool may be associated 1:1. A PSSCH resource pool mayinclude one subchannel or a plurality of subchannels in the frequencydomain. A subchannel may include consecutive resource blocks in the samesubframe and may be predetermined or may be set by the BS. The maximumnumber of subchannels in one subframe may be 20. The minimum size (thenumber of resource blocks) of a subchannel may be four. The PSCCHresource pool may include consecutive PRBs.

The energy sensing granularity of a PSSCH may be the size of asubchannel.

The UE may always select an integer number of contiguous subchannels fortransmission.

The UE does not attempt to decode more than 100 resource blocks in onesubframe and does not attempt to decode more than 10 PSCCHs.

The SA resource pool and the data resource pool may overlap.

The resource pool for V2V may be defined by a bitmap mapped to subframesother than a subframe for transmitting an SLSS. The length of the bitmapmay be any one of 15, 20, and 100. The bitmap may indicate/define asubframe in which SA/data transmission/reception for V2V is allowed.

When resource reselection is triggered, the UE reselects resources forall transmissions corresponding to a transmission block. An SA schedulesonly transmission corresponding to one transmission block.

Hereinafter, (A) an SCI format configuration field(s) used in a mode-2V2V scheduling (MODE2_SCH) operation and/or (B) a DCI formatconfiguration field(s) used in a mode-1 dynamic V2V scheduling(MODE1_DYN) will be described. Here, mode 1 is a mode in which a BSschedules a resource for V2V communication, and mode 2 is a mode inwhich a UE selects a resource for V2V communication from a resource poolset by a network or predetermined.

SCI may be control information transmitted by a UE in a sidelink, may be48 bits in total, and may include the following fields.

Priority: 3 bits, resource reservation: 4 bits, MCS: 5 bits, CRC: 16bits, retransmission index: 1 bit, time gap between initial transmissionand retransmission: 4 bits (Here, this field has one value of 0 to 15,in which 0 denotes no retransmission of a related transmission block),frequency resource location (FRA_INRETX) for initial transmission andretransmission: 8 bits, reserved bits: 7 bits. RV 0 and 2 aresequentially used for initial transmission and retransmission.

DCI transmitted by a BS for dynamic scheduling for a sidelink mayinclude the following fields.

CIF: 3 bits (an interpretation of the CIF may be preset and may bedifferent from that of a CIF for uplink and downlink), lowest (smallest)index of subchannel assigned for initial transmission (PSCCH_RA): 5bits, SA content: i) time gap between initial transmission andretransmission (TGAP_INRETX: 4 bits), ii) frequency resource locationfor initial transmission and retransmission (FRA_INRETX: 8 bits). Thelength of the DCI may be the same as DCI format 0, and an RNTI otherthan a C-RNTI/SPS-RNTI may be used. A time location for initialtransmission may be the first subframe included in a resource pool of aV2V carrier and may be a subframe 4 ms after a subframe in which the DCIis transmitted.

It is assumed that the maximum number of subchannels (referred to asSF_MAXNUMSCH), which can be included in a V2V resource pool, in onesubframe is (always) 20, the payload size of a MODE1_DYN DCI format maybe a total of 20 bits (e.g. “3 (=CIF)+5 (=PSCCH_RA)+4 (=TGAP_INRETX)+8(=FRA_INRETX)=20”).

When the payload size of the MODI1_DYN DCI format is matched to that ofexisting DCI format 0, the payload size of the MODI1_DYN DCI format(e.g., 20 bits) may become greater than that of DCI format 0 (e.g., 19bits (1.4 MHz)) at a particular system bandwidth (e.g., 1.4 MHz). Tosolve this problem, (some) methods are proposed as follows.

For example, a V2V (PSSCH (/PSCCH)) resource pool may be configured by(information) signaling (A) the total number of subchannels included inthe V2V resource pool in one subframe, and/or (B) the number of resourceblocks included in a (single) subchannel (subchannel size), and/or (C)the starting location of a subchannel (RB) in the frequency domain,and/or (D) the location of a subframe where the V2V resource pool is set(e.g., a predefined length (e.g., a bitmap format of 16, 20, or 100))(and/or (E) the starting location of a subchannel (RB) (in the frequencydomain) of a (E)PSCCH resource pool (this information may be valid(present) only when a PSCCH and a (linked) PSSCH are not located oncontiguous resource blocks in the same subframe)).

The following (some) proposed methods may be extended to (determinationof FRA_INRETX size in) an SCI format associated with the MODE2_SCHoperation.

The following table illustrates the payload size of existing DCI format0 in each system bandwidth.

TABLE 1 DCI format 0 Bandwidth 1.4 MHz 3 MHz 5 MHz 10 MHz 15 MHz 20 MHzHopping flag 1 1 1 1 1 1 N_ULHOP 1 1 1 2 2 2 Resource block assignment 57 7 11 12 13 MCS & RV 5 5 5 5 5 5 NDI 1 1 1 1 1 1 TPC for PUSCH 2 2 2 22 2 Cyclic shift for DMRS 3 3 3 3 3 3 CQI request 1 1 1 1 1 1 Total bits19 21 21 26 27 28

[Proposed method #1] For example, the size of FRA_INRETX (and/orPSCCH_RA) included in DCI format 5A can be changed depending on thetotal number of subchannels (TSUBNUM_SF) included in a V2V resource pool(in one subframe) set (signaled) in advance. Here, DCI format 5A is aDCI format used for PSCCH scheduling and may also include fields usedfor PSSCH scheduling.

FIG. 9 illustrates a method for determining the payload size of DCIformat 5A according to proposed method #1.

Referring to FIG. 9, a BS may determine the number of subchannels(=TSUBNUM_SF) of a V2V resource pool in a subframe (S100) and may changethe payload size (frequency resource location field for initialtransmission and retransmission) of DCI format 5A according to thenumber of subchannels (TSUBNUM_SF) (S110). Here, a subchannel mayinclude a plurality of contiguous resource blocks in the same subframe.For example, the BS may adjust the number of resource blocks included ina subchannel, thereby adjusting the size of a resource allocation (RA)field of DCI format 5A. Accordingly, it is possible to prevent the totalpayload size of DCI format 5A from being greater than that of DCI format0.

For example, when the total number of subchannels (TSUBNUM_SF) includedin a V2V resource pool within one subframe is K, the size of FRA_INRETX(frequency resource location field for initial transmission andretransmission) (and/or PSCCH_RA (lowest (smallest) index field of asubchannel assigned for initial transmission)) included in DCI format 5Amay be CEILING(LOG₂(K·(K+1)/2)) (and/or “CEILING (LOG₂(K))”). Here,CEILING(X) is a function for deriving a minimum integer value that isequal to or greater than X.

For example, when the total number of subchannels (TSUBNUM_SF) includedin a V2V resource pool within one subframe is 10, the size of FRA_INRETX(and/or PSCCH_RA) may be six bits (and/or four bits).

When this rule is applied, TSUBNUM_SF (number of subchannels) isproperly set (signaled) (by a network), thereby solving the foregoingproblem such that the payload size (e.g., 20 bits) of the MODE1_DYN DCIformat is greater than the payload size (e.g. 19 bits) of existing DCIformat 0 in a 1.4 MHz system bandwidth.

For example, the size of FRA_INRETX (and/or PSCCH_RA) can be changedaccording to the FLOOR value (the number of resource blocks included ina system bandwidth/(one) subchannel (subchannel size)) (which isreferred to as MAX_SUBVAL). Here, FLOOR(X) is a function for deriving amaximum integer value that is less than or equal to X.

For example, when MAX_SUBVAL=K, the size of FRA_INRETX (and/or PSCCH_RA)may be changed to CEILING(LOG₂(K·(K+1)/2)) (and/or CEILING (LOG₂(K))).

[Proposed method #2] For example, (when proposed method #1 is applied)remaining bits of “(payload size of (existing) DCI format0−CEILING(LOG₂(K(K+1)/2)) (=FRA_INRETXsize)−3(=CIF)−5(=PSCCH_RA)−4(=TGAP_INRETX))” (and/or remaining bits of“(payload size of (existing) DCI format 0−CEILING(LOG₂(K(K+1)/2))(=FRA_INRETX size)−3(=CIF)−CEILING(LOG₂(K))(=PSCCH_RAsize)−4(=TGAP_INRETX)” can be set to a value (e.g., 0 or 1) designatedby a (serving) BS (or network) through predefined(higher/physical)-layer (e.g., SIB or RRC) signaling or may be (always)padded with zeros (by a UE). The remaining bits may be used as a virtualCRC.

The application of (some of) this rule may be interpreted such thatadditional extra bits, which occur when the FRA_INRETX size is changedaccording to proposed method #1 (in MODE1_DYN DCI format and/orMODE2_SCH SCI format), (e.g., “(8−CEILING(LOG₂(K·(K+1)/2)) (=FRA_INRETXsize))” (and/or “(8−CEILING(LOG₂(K·(K+1)/2)) (=FRA_INRETXsize)−CEILING(LOG₂(K))(=PSCCH_RA size))”)) (and/or the (target) payloadsize predefined (signaled) (e.g., (additional) extra bits, which occurwhen the FRA_INRETX size is changed according to proposed method #1, the(target) payload size in MODE1_DYN DCI format and the (target) payloadsize in MODE2_SCH SCI format may be the payload size of (existing) DCIformat 0, which is 48 bits) may be set to a value designated by a(serving) BS (or network) through predefined (higher/physical)-layersignaling or may be (always) padded with zeros (by a UE).

When proposed method #1 is applied, if an (mode-1) SPS operation-relatedfield (e.g., SPS configuration (/activation(/release)) indicator)(SPS_PALD) needs to be further defined in a MODE1_DYN operation-relatedDCI format, a TSUBNUM_SF value may be (limitedly) set (/signaled) when acondition is satisfied that remaining bits of “(payload size of(existing) DCI format 0−CEILING(LOG₂(K·(K+1)/2))(=FRA_INRETXsize)−3(=CIF)−5(=PSCCH_RA)−4(=TGAP_INRETX)−SPS_PALD size)” (and/orremaining bits of “(payload size of (existing) DCI format0−CEILING(LOG₂(K·(K+1)/2))(=FRA_INRETXsize)−3(=CIF)−CEILING(LOG₂(K))(=PSCCH_RA size)−4(=TGAP_INRETX)−SPS_PALDsize)” is greater than 0.

A MODE1_DYN operation-related DCI format (M1DYN_DCI) may be managedaccording to (some of) the following rules. Here, (some of) the rulesmay also be applied to a mode-1 V2V SPS operation-related DCI format.

[Proposed method #3] When cross-carrier scheduling (CCS) M1DYN_DCI for aparticular frequency (cell) (referred to as SD_CELL) is transmitted on asearch space (SS) of (another) particular frequency (cell) (referred toas SC_CELL) that is preset (/signaled), the payload size of CCSM1DYN_DCI can be matched to the (payload) size (SC_FMOLN) of a preset(/signaled) DCI format (e.g., DCI format 0) based on an SC_CELL-relatedparameter (not to the (payload) size (SD_FMOLN) of a preset (/signaled)DCI format (e.g., DCI format 0) based on an SD_CELL-related parameter(e.g., system (uplink) bandwidth)).

Here, the search space of the (other) particular frequency (cell)(SC_CELL), on which SD_CELL-related M1DYN_DCI is transmitted, may beconstrued as a search space that is located on (another)(preset/signaled) particular frequency (cell) for cross-carrierscheduling of SC_CELL and transmits cross-carrier scheduling informationrelated to the (other) particular frequency (cell) (SC_CELL) SS.

For example, when the (payload) size of CCS M1DYN_DCI is smaller thanSC_FMOLN, zero padding may be performed such that the (payload) sizeequals SC_FMOLN.

FIG. 10 illustrate a size fitting, method for DCI format 1A according tothe prior art.

Referring to FIG. 10, a first search space 121 for DCI to schedulesecondary cell #1 (Scell #1) and a second search space 122 for DCI toschedule secondary cell #2 (Scell 42) may be determined within a PDCCHregion for a primary cell. A carrier indication field (CIF) for Scell #1is N and a CIF for Scell #2 is M, where N and M may be differentintegers.

In this case, DCI format 1A for Scell #1 in the first search space 121is size-fitted to the size of DCI format 0 for Scell #1. DCI format 1Afor Scell #2 in the second search space 122 is size-fitted to the sizeof DCI format 0 for Scell #2. That is, when the number of informationbits of DCI format 1A mapped to a given search space is less than thatof DCI format 0 that is mapped to the search space and schedules thesame serving cell, zero padding is performed so that DCI format 1A hasthe same size as that of DCI format 0.

FIG. 11 conceptually illustrates a size fitting method for DCI format 5AAccording to proposed method #3.

Referring to FIG. 11, DCI format 0 for Scell #1 and DCI format 5A for aV2V carrier may share the same search space. For example, when a CIF forScell #1 and a CIF for the V2V carrier are set to have the same value(=N), the search spaces may be set to be common.

In this case, DCI format 5A for the V2V carrier undergoes zero padding(i.e. size fitting) to match the size of DCI format 0 that shares thesame search space regardless of whether the formats (the DCI format 5Aand the DCI format 0) are for the same serving cell, That is, eventhough the same search space is shared with DCI format 0 for a differentcell, the size of DCI format 5A for the V2V carrier is matched to thesize of DCI format 0 for the different cell.

FIG. 12 illustrates a generalized size fitting method for a DCI formataccording to proposed method #3.

Referring to FIG. 12, a BS may determine the size of a first DCI format(S20), may fit the size of a second DCI format (zero padding) to thesize of the first DCI format (S21), and may transmit the second DCIformat to a UE. The first DCI format and the second DCI format may beDCI formats that share the same search space regardless of whether theformats are for the same serving cell. That is, the first DCI format andthe second DCI format may be DCI formats for scheduling physicalchannels of different serving cells.

The first DCI format and the second DCI format may have the same CIFvalue and may thus share the same search space. That is, the first DCIformat and the second DCI format may be mapped to the same search space.

FIG. 13 illustrates a specific example of applying FIG. 12.

Referring to FIG. 13, a BS may determine the size of DCI format 0(S200), may fit the size of DCI format 5A (zero padding) to the size ofDCI format 0 (S210), and may transmit DCI format 5A to a UE, Asdescribed above, DCI format 0 is a DCI format used to schedule aphysical uplink shared channel (PUSCH), and DCI format SA is a DCIformat used to schedule a physical sidelink control channel (PSCCH) andmay also include fields for PSSCH scheduling.

Meanwhile, when the foregoing rule is applied, the UE may (always)assume (/expect) that the (payload) size of CCS M1DYN_DCI before zeropadding on the SC_CELL SS is not greater than SC_FMOLN (e.g., DCI format0). Further/alternatively, it may be interpreted that a network (always)configures (/signals) (or guarantees (by adjusting the number ofsubchannels included in a V2X resource pool)) the (payload) size of CCSM1DYN_DCI before zero padding on the SC_CELL SS not to be greater thanSC_FMOLN.

In determining and retrieving for DCI formats to be retrieved in asearch space, the UE may retrieve DCI format SA assuming that the sizeof DCI format SA is equal to the size of DCI format 0 sharing the searchspace with DCI format SA.

FIG. 14 illustrates an operation method of a UE in a search space.

Referring to FIG. 14, the UE may determine the size of DCI format 0 in agiven search space (S400) and may not expect (attempt) to detect DCIformat 5A having a size larger than the size of DCI format 0 in thesearch space (S410).

CCS M1DYN_DCI(s) related to a plurality of preset (/signaled) SD_CELL(s)transmitted on an SC_CELL search space may be considered to betransmitted, regardless of the value of each CIF, in a SC_CELL-relatedUE-specific search space (USS) (and/or common search space (CSS)) (ortransmitted in an (individual) SD_CELL-related USS (and/or CSS) (onSC_CELL) derived by a search space equation having a CIF value as aninput parameter (e.g., when the SD_CELL-related CCS M1DYN_DCI istransmitted on the SC_CELL SS, it may be considered that SD_CELL andSC_CELL have the same CIF value)).

For example, a CIF (e.g., 3 bits) of particular frequency (cell)-relatedM1DYN_DCI may be defined to be always included regardless of whether aCCS operations is configured (/applied).

Here, when this rule is applied, the payload size of M1DYN_DCItransmitted in a frequency (/cell) (SF_CELL) to which a self-scheduling(SFS) MODE1_DYN operation is applied may be matched to the (payload)size of a DCI format (e.g., DCI FORMAT 0) preset (/signaled) based on anSF_CELL-related parameter (e.g., system (uplink) bandwidth) in theabsence of a CIF (or in the case where a CCS operation is notconfigured).

((Preset (/signaled)) (a plurality of) SD_CELL(s)-related) CCSM1DYN_DCI(s) may be transmitted only in a particular preset (/signaled)frequency (/cell) (e.g., primary frequency (/cell) or secondaryfrequency (/cell)) (USS (and/or CSS)) and/or a particular preset(/signaled) frequency (/cell)-related CIF value may be (always) set to 0(or a particular preset (/signaled) value).

For example, a linkage between a CIF value for a frequency (/cell) inwhich V2X communication (/operation) is performed and a CIF value for afrequency (/cell) in which WAN (UL) communication (/operation) isperformed may be set through predefined higher (/physical)-layersignaling.

When this rule is applied, V2X DCI related to the frequency (/cell)where V2X communication (/operation) is performed, which is related tothe set linkage, may be (blind-) detected in a search space related tothe frequency (/cell) where WAN (UL) communication (/operation) isperformed. Further/alternatively, it may be interpreted that WAN (UL)DCI related to the frequency (/cell) where WAN (UL) communication(/operation) is performed, which is related to the set linkage, may beblind-detected in an SS related to the frequency (/cell) where V2Vcommunication (/operation) is performed.

Hereinafter, structures and (payload) sizes for mode-1 sidelink dynamicscheduling DCI (MODE1_SLDYNDCI) and/or mode-1 sidelink semi-persistentscheduling DCI (MODE1_SLSPSDCI) and/or mode-1 uplink semi-persistentscheduling DCI (MODE1_ULSPSDCI) will be described.

A DCIs-related size-fitting operation may be performed according to(some of) the following rules. Here, (some of) the following rules maybe limitedly applied only when a mode-1 sidelink dynamic scheduling(MODE1_SLDYN) operation and/or a mode-1 sidelink semi-persistentscheduling (MODE1_SLSPS) operation are simultaneously set (/signaled)for one V2X UE with respect to one particular carrier/frequency.

Hereinafter, for the convenience of description, a carrier (/frequency)where a MODE1_SLDYN operation and/or a MODE1_SLSPS operation areperformed is referred to as “V2X_CARRIER”, and a carrier (/frequency)where related cross-carrier scheduling (CCS) DCI is transmitted isreferred to as “SCH_CARRIER”. “SCH_CARRIER” may also be referred to as,for example, “WAN (UL) carrier (/frequency)” (e.g., primary cell(/secondary cell)).

V2X_CARRIER and SCH_CARRIER may be different carriers in cross-carrierscheduling or may be the same carrier in self-scheduling (SFS).

In the present invention, the term “carrier” may be (extended to)interpreted as “cell” and/or “component carrier”.

The mode-1 sidelink dynamic scheduling DCI (MODE1_SLDYNDCI) may includethe following fields:

1) CIF which occupies 3 bits; 2) lowest index of assigned subchannel,which may be obtained by Ceil(log₂(k) and may occupy one of 0 to 5 bits;3) time gap between initial transmission and retransmission whichoccupies 4 bits; and 4) frequency resources for initial transmission andlast transmission, which may be obtained by Ceil(log₂(k*(k+1)/2) and mayoccupy one of 0 to 8 bits.

When the number of information bits in a V2V DCI format mapped to agiven search space is less than the payload size of DCI format 0 that ismapped to the same search space, zeros are appended to the V2V DCIformat until the V2V DCI format has the same size as that of DCI format0 (including padding bits if present).

The mode-1 sidelink semi-persistent scheduling DCI (MODE1_SLSPSDCI) mayinclude the following fields.

MODE1_SLSPSDCI may further include the following two fields in additionto fields included in existing dynamic scheduling DCI (e.g., DCI 5A): 1)sidelink SPS configuration index which occupies 3 bits; and 2)activation/release indication which occupies 1 bit. Theactivation/release indication may indicate activation/release of asidelink SPS. A RNTI (SL SPS RNTI) different from a sidelink dynamicscheduling RNTI may be defined.

MODE1_SLSPSDCI may include one SPS configuration index.

When the number of information bits in a sidelink semi-persistentscheduling DCI format mapped to a given search space is less than thepayload size of DCI format 0 that is mapped to the same search space,zeros are appended to the sidelink semi-persistent scheduling DCI untilthe sidelink semi-persistent scheduling DCI has the same size as that ofDCI format 0 (including padding bits if present).

The mode-1 uplink semi-persistent scheduling DCI (MODE1_ULSPSDCI) mayreuse a particular field included in DCI format 0, for example, a cyclicshift DM RS (3 bits) field or a TPC command (2 bits) field, to indicatea V2X UL SPS configuration index.

The mode-1 uplink semi-persistent scheduling DCI may include one SPSconfiguration index.

[Proposed method #4] In one example, when at least one of MODE1_SLDYNDCIand MODE1_SLSPSDCI is transmitted via a search space in SCH_CARRIERwhere WAN (UL) communication (carrier (/frequency))-related DCI FORMAT 0is transmitted (or, conversely, WAN (UL) communication (carrier(/frequency))-related DCI FORMAT 0 is transmitted (/present) in a searchspace in SCH_CARRIER in which at least one of MODE1_SLDYNDCI andMODE1_SLSPSDCI is transmitted), at least one of the followingillustrative methods may be employed.

(Example #4-1) All or only (particular) predefined or signaled DCI(e.g., MODE1_SLDYNDCI)) among MODE1_SLDYNDCI, MODE1_SLSPSDCI, and DCIFORMAT 0 may be size-fitted to the largest payload size (e.g., the sizeof MODE1_SLSPSDCI or DCI FORMAT 0) among the payload sizes of the abovethree pieces of DCI.

(Example #4-2) The payload size of (only) MODE1_SLDYNDCI may besize-fitted to that of MODE1_SLSPSDCI. For example, when the payloadsize of DCI FORMAT 0 is smaller than that of MODE1_SLSPSDCI (and/orMODE1_SLDYNDCI), the payload size of (only) MODE1_SLDYNDCI may besize-fitted to that of MODE1_SLSPSDCI.

(Example #4-3) the payload size of all of MODE1_SLDYNDCI and/orMODE1_SLSPSDCI and/or DCI FORMAT 0 may be size-fitted to the payloadsize of particular preset (/signaled) DCI format (e.g., MODE1_SLSPSDCIor DCI FORMAT 0).

The search space in the scheduling carrier (SCH_CARRIER) in which thesidelink dynamic scheduling DCI (MODE1_SLDYNDCI) and/or the sidelinksemi-persistent scheduling DCI (MODE1_SLSPSDCI) are transmitted isderived using a V2X_CARRIER-related CIF value. DCI FORMAT 0 may beconstrued as a particular preset (/signaled) reference DCI format forsize fitting related to MODE1_SLDYNDCI and/or MODE1_SLSPSDCI transmittedon the same search space.

In another example, when MODE1_SLDYNDCI and/or MODE1_SLSPSDCI aretransmitted via a search space in SCH_CARRIER where a reference DCIformat (e.g., DCI format 0) is not transmitted (or, conversely, areference DCI format is not transmitted (/present) in a search space inSCH_CARRIER where MODE1_SLDYNDCI and/or MODE1_SLSPSDCI are transmitted),at least one of the following illustrative methods may be employed.

(Example #4-4) The payload size of MODE1_SLDYNDCI may be size-fitted toa relatively large size of MODE1_SLSPSDCI. For example, the payload sizeof MODE1_SLSPSDCI may be greater by four bits than that ofMODE1_SLDYNDCI.

FIG. 15 illustrate a DCI size fitting method according to example #4-4.

Referring to FIG. 15, when a predefined reference DCI format (e.g., DCIformat 0) is not present in a search space where sidelinksemi-persistent scheduling DCI and sidelink dynamic scheduling DCI aretransmitted, a BS may determine the size of the sidelink semi-persistentscheduling DCI (S300) and may fit the size of the sidelink dynamicscheduling DCI to the size of the sidelink semi-persistent schedulingDCI (S310).

That is, when the sidelink semi-persistent scheduling DCI and thesidelink dynamic scheduling DCI are transmitted in a search space on ascheduling carrier where DCI format 0 is not transmitted, the size ofthe sidelink dynamic scheduling DCI is fitted to the size of thesidelink semi-persistent scheduling DCI. According to this method, it ispossible to reduce the number of times a UE performs blind decoding andto reduce complexity.

(Example #4-5) Considering V2X_CARRIER as a virtual WAN (UL)communication carrier (/frequency), the payload size (VIR_DCIZSIZE) ofDCI format 0 (or MODE1_SLSPSDCI) is derived on the basis of at least oneof the payload size of DCI format 0 based on a V2X_CARRIER (system)bandwidth, the payload size of DCI format 0 based on a SCH_CARRIER(system) bandwidth (where WAN (UL(/DL)) communication is performed), thepreset (/allowed) greatest (system) bandwidth (e.g., 20 MHz), and anominal system bandwidth, the maximum number of subchannels (e.g., 20,or nominal subchannel number). Subsequently, the payload size of (allof) MODE1_SLDYNDCI and/or MODE1_SLSPSDCI (A) may be size-fitted toVIR_DCIZSIZE and/or (B) may be size-fitted to the largest payload sizeamong the sizes of MODE1_SLDYNDCI and/or the size of MODE1_SLSPSDCIand/or VIR_DCIZSIZE.

(Example #4-6) The payload size of (all of) MODE1_SLDYNDCI and/orMODE1_SLSPSDCI may be size-fitted to the payload size of a particularpreset (/signaled) DCI format.

Here, for example, duplex mode (e.g., TDD/FDD) information assumed(/applied) in calculating a reference DCI (payload) size (e.g.,VIR_DCIZSIZE) for size fitting (of MODE1_SLDYNDCI and/or MODE1_SLSPSDCI)may be assumed (/considered) (A) to be the same as that of a systembandwidth (value) reference carrier (or V2X_CARRIER or SCH_CARRIER)and/or (B) to be a preset (/signaled) nominal duplex mode. For example,(since the payload size of DCI format 0 is smaller than that ofMODE1_SLDYNDCI and/or MODE1_SLSPSDCI (and/or VIR_DCIZSIZE)), when thepayload size of DCI format 0 should be increased (for size fitting), thepayload size of DCI format 1A (transmitted in the same SS) may besize-fit to the increased payload size of DCI format 0.

In still another example, an additional field indicating information onthe time location of a scheduled V2X subframe may be defined inMODE1_SLDYNDCI and/or MODE1_SLSPSDCI so that all subframes in a preset(/signaled) V2X resource pool on V2X_CARRIER are (cross-carrier-)scheduled (from a (TDD) UU carrier). This field may be, for example, 2bits and may be referred to as TL_FIELD. A UU carrier refers to acarrier used between a BS and a UE.

The size of TL_FIELD may be fixed to a preset (/signaled) value (K_SIZE)(regardless of the TDD UL-DL configuration of the (TDD) UU carrier).Here, the size of actually used bits in K_SIZE may be differently (orindependently) set (/signaled) for each TDD UL-DL configuration of a(TDD) UU carrier.

For example, bits actually not used in K_SIZE may be designated to be apreset (/signaled) value (e.g., 0) or may be used as a virtual CRC).Further/alternatively, bits actually not used in K_SIZE may bedesignated by a V2X UE to be a random value in order to obtainadditional randomization effect of a PSSCH DM-RS sequence (/cyclicshift) (derived with a PSCCH CRC value).

When (cross-carrier scheduling) MODE1_SLDYNDCI and/or MODE1_SLSPSDCIincluding TL_FIELD are received in subframe #4 (SF #N) (on the (TDD) UUcarrier), in which TL_FIELD indicates K, scheduling information-basedinitial transmission time may be the closest (K+1)th V2X subframebelonging to the (preset (/signaled)) V2X resource pool after 4 ms (foursubframes) from the reception time (SF #N) of (cross-carrier scheduling)MODE1_SLDYNDCI and/or MODE1_SLSPSDCI.

In the above rule, the TL_FIELD size (and/or actually used bits inK_SIZE) may be differently set (/signaled) depending on the TDD UL-DLconfiguration of a (TDD) UU carrier (and/or (V2X transmission-related)scheduling type (e.g., self-carrier scheduling and cross-carrierscheduling)).

The foregoing rules may be extended to V2X UL SPS DCI in order toincrease the degree of freedom in designating (/scheduling) V2X UL SPSactivation (/release) time.

For example, when (cross-carrier scheduling) V2X UL activation(/release) SPS DCI including TL_FIELD is received in SF #N (on the (TDD)UU carrier), in which TL_FIELD indicates K, V2X UL activation (/release)application time may be the closest (K+1)th UL subframe after 4 ms (foursubframes) from the reception time (SF #N) of the (cross-carrierscheduling) V2X UL activation (/release) SPS DCI.

FIG. 16 illustrates sidelink cross-carrier scheduling timing.

Referring to FIG. 16, a Uu carrier is set to TDD UL-DL configuration #0.

As illustrated in FIG. 16, when DCI is received in subframe #n (downlinksubframe or special subframe) of the Uu carrier and subframe #n+4 of aPC5 carrier is scheduled by the DCI, it is impossible to schedule allsubframes of the PC5 carrier. Therefore, in TDD, a field to indicate thetime location of a V2V subframe scheduled may be added.

Hereinafter, examples of (A) the field configuration of a mode-1sidelink dynamic scheduling DCI format (SLDYN_DCI) (e.g., DCI format 5A)and/or (B) the field configuration of a mode-1 sidelink SPS DCI format(SLSPS_DCI) and/or (C) the field configuration of an SCI format(SCI_FMT) (e.g., SCI format 1) will be described.

When a mode-1 sidelink SPS operation is performed, a UE may be allowedto set the value of a resource reservation field (which may be a fieldindicating a resource reservation period value or a V2X messagetransmission period value for a V2X transmission UE) of an SCI formataccording to (some of) the following rules.

First, DCI format 5A (SLDYN_DCI) is used for PSCCH scheduling mayinclude the following information or fields:

1) carrier indication field (3 bits); 2) lowest index of subchannelallocation (which may occupy ceil(log₂(N^(SL) _(subchannel))) bits); 3)SCI format 1 fields; 4) sidelink index (2 bits, which may be presentonly for cases with TDD operation with UL-DL configuration 0-6).

The SCI format 1 fields may include: 1) a field of frequency resourcelocation for initial transmission and retransmission; and 2) a field oftime gap between initial transmission and retransmission.

When the number of information bits in DCI format 5A mapped to a givensearch space is less than the payload size of DCI format 0 that ismapped to the same search space, zeros are appended to DCI format 5Auntil DCI format 5A has the same size as that of DCI format 0 (includingpadding bits if present).

The sidelink SPS DCI (SLSPS_DCI) may further include fields of: 1)sidelink SPS configuration index (3 bits); and 2) activation/releaseindication (1 bit) in addition to the fields included in the dynamicscheduling DCI (i.e., DCI format 5A).

SCI format 1 (SCI_FMT) is used for PSSCH scheduling and may include thefollowing information bits or fields:

1) priority (3 bits); 2) resource reservation (4 bits); 3) frequencyresource location for initial transmission and retransmission (which mayoccupy ceil(log₂(N^(SL) _(subchannel)(N^(SL) _(subchannel)+1)/2) bits);4) time gap between initial transmission and retransmission (4 bits); 5)modulation and coding scheme (5 bits); and 6) retransmission index (1bit). Meanwhile, reserved information bits are added until the size ofSCI format 1 is equal to 32 bits.

[Proposed method #5] When a BS performs (particular) sidelink SPSconfiguration (index) (SLSPSCON #X) activation and/or (SLSPSCON#X-related) (periodic) resource reservation for V2X transmission UE #Kthrough SLSPS_DCI, if transmitting a V2X message using some or all of(SLSPSCON #X-related) (periodic) resources, V2X transmission UE #K maybe allowed to set the value of a resource reservation field in SCI_FMT(A) to an SLSPSCON #X-related period value ((RRC-) signaled in advancefrom the BS) and/or (B) to a value (preset (/signaled) or configured bythe UE), instead of a (carrier-specific candidate) value configurable asa resource reservation field value, thus notifying another V2X UE thatthe UE transmits a V2X message based on mode 1 (and/or mode 1 sidelinkSPS), and/or (C) to a (random) value configured by the UE. Here, therules (B) and/or (C) may be (limitedly) applied only when a resourcepool related to mode 1 (and/or mode 1 sidelink SPS) is set (/signaled)to be different from that for another mode (e.g., mode 2).

The illustrative proposed methods described above may also be includedas methods for implementing the present invention and thus may beregarded as a kind of proposed schemes. In addition, the proposedmethods described above may be implemented independently, but some ofthe proposed methods may be combined (or merged) for implementation.

Although the present invention has been described with reference to theproposed methods based on 3GPP LTE/LTE-A systems for the convenience ofdescription, the scope of systems to which the proposed methods areapplied may be extended to other systems besides the 3GPP LTE/LTE-Asystems.

The proposed methods of the present invention may also be extended forD2D communication. Here, D2D communication refers to communicationbetween one UE and another UE via a direct wireless channel. A UE may bea terminal of a user. Further, when network equipment, such as a BS,transmits or receives a signal according to the communication modebetween UEs, the network equipment may also be regarded as a UE.

The proposed methods of the present invention may be applied only to amode-2 V2X operation (and/or mode-1 (sidelink dynamic scheduling and/orsidelink SPS and/or uplink SPS) V2X operation).

The proposed methods of the present invention may be limitedly appliedonly when a PSCCH and a (linked) PSSCH are not located (or are located)in contiguous resource blocks in the same subframe.

In addition, the proposed methods of the present invention may also beapplied not only to a V2V mode-1 (/mode-2) dynamic scheduling operationbut also to a V2V mode-1 (/mode-2) semi-static scheduling (SPS)operation (and/or a V2X mode-1 (/mode-2) dynamic scheduling operationand/or a V2X mode-1 (/mode-2) SPS operation).

In the present invention, the term “mode 1” (or “mode 2”) may beinterpreted as (/replaced with) “mode 3” (or “mode 4”) related to V2Xcommunication.

(All or some of) The proposed methods of the present invention may beapplied to DCI and/or SCI associated with V2X communication.

FIG. 17 is a block diagram illustrating a device to implement anembodiment of the present invention.

Referring to FIG. 17, the device 1100 includes a processor 1110, amemory 1120, and a radio frequency (RF) unit 1130. The device 1100 maybe a base station, a relay station, or a UE. The processor 1110 performsa proposed function, process and/or method.

The RF unit 1130 is connected to the processor 1110 and transmits andreceives radio signals. The memory 1120 may store information necessaryfor driving the processor 1110 and/or the RF unit 1130.

The processor may comprise an application-specific integrated circuit(ASIC), other chipset, logic circuitry and/or data processing device.The memory may include read-only memory (ROM), random access memory(RAM), flash memory, memory cards, storage media, and/or other storagedevices. The RF unit may include a baseband circuit for processing theradio signal. When the embodiment is implemented in software, theabove-described techniques may be implemented with modules (processes,functions, and so on) that perform the functions described above. Themodule may be stored in the memory and may be executed by the processor.The memory may be internal or external to the processor, and may becoupled to the processor by various well known means.

What is claimed is:
 1. A method of receiving downlink controlinformation (DCI) by a user equipment (UE) in a wireless communicationsystem, the method comprising: receiving i) a first DCI format used forsidelink semi-persistent scheduling or ii) a second DCI format used forsidelink dynamic scheduling; and operating based on the received DCI,wherein the first DCI format and the second DCI format are DCI formatssharing a search space in which a reference DCI format related to acommunication between the UE and a base station is not present.
 2. Themethod of claim 1, wherein a bit size of the first DCI format is equalto a bit size of the second DCI format.
 3. The method of claim 1,wherein the first DCI format and the second DCI format are DCI formatsrelated to a communication between the UE and another UE.
 4. A userequipment (UE), the UE comprising: a radio frequency (RF) unit totransmit and receive a radio signal; and a processor connected to the RFunit, wherein the processor is configured to: receive i) a first DCIformat used for sidelink semi-persistent scheduling or ii) a second DCIformat used for sidelink dynamic scheduling; and operate based on thereceived DCI, wherein the first DCI format and the second DCI format areDCI formats sharing a search space in which a reference DCI formatrelated to a communication between the UE and a base station is notpresent.
 5. The UE of claim 4, wherein a bit size of the first DCIformat is equal to a bit size of the second DCI format.
 6. The UE ofclaim 4, wherein the first DCI format and the second DCI format are DCIformats related to a communication between the UE and another UE.
 7. Anapparatus for receiving downlink control information (DCI) in a wirelesscommunication system, the apparatus comprising: at least one memory; andat least one processor connected to the at least one memory, wherein theprocessor is configured to: receive i) a first DCI format used forsidelink semi-persistent scheduling or ii) a second DCI format used forsidelink dynamic scheduling; and operate based on the received DCI,wherein the first DCI format and the second DCI format are DCI formatssharing a search space in which a reference DCI format related to acommunication between the UE and a base station is not present.
 8. Theapparatus of claim 7, wherein a bit size of the first DCI format isequal to a bit size of the second DCI format.
 9. The apparatus of claim7, wherein the first DCI format and the second DCI format are DCIformats related to a communication between the UE and another UE.